JABLONSKI, D.; Univ. of Chicago: Evolutionary Innovations in the Fossil Record: Patterns in time and space

The origin of evolutionary innovations has been intensively studied, but relatively little is known about ecological and biogeographic patterns in the first occurrences of major groups or innovations. In post-Paleozoic marine fossil record, new orders do not originate randomly with respect to environment or latitude. Instead, when preservation and sampling are taken into account, new orders tend to appear first in onshore, disturbed habitats and in the tropics. The environmental pattern occurs even in groups that are now exclusively deep-water, such as isocrinid crinoids and holasteroid echinoids, and can be recognized in terms of excursions in morphospace without reference to taxonomic categories. The environmental pattern at high levels also contrasts significantly with the origin of low-level novelties (such as define genera and families) in crinoids, echinoids, and bryozoans, where first appearances tend to conform to their clade-specific bathymetric diversity gradients. The geographic pattern faces even greater sampling problems, but major groups first occur disproportionately in the tropics. Still controversial is whether these patterns are primarily genetic and developmental, i.e. innovations truly arise onshore and in tropical settings; or are primarily ecological, i.e. innovations arise randomly but preferentially survive onshore and in the tropics. Whatever the ultimate driving mechanisms, these results show that ecology and biogeography must enter into theories of large-scale evolutionary novelty.